Processes for recycling used or in-process defective batteries (hereinafter referred to as “waste batteries”), such as waste lithium-ion batteries, and recovering their valuable metals are broadly divided into dry and wet processes.
A dry process includes melting crushed waste batteries, separating valuable metals, which are to be recovered, from other less valuable metals and materials by harnessing the difference in oxygen affinity between them, and recovering the valuable metals. Specifically, such a dry process includes oxidizing less valuable elements, such as iron, as much as possible to form slag and suppressing the oxidation of valuable materials, such as cobalt, as much as possible to recover the valuable materials in the form of an alloy.
For example, Patent Document 1 discloses adding a SiO2/CaO-based flux to waste batteries and recovering, from the mixture, valuable metals such as nickel and cobalt in the form of an alloy using a high-temperature heating furnace, wherein the resulting slag has a composition containing at least 20% iron, calculated as metallic iron, and at most 20% of each of nickel and cobalt, and having an SiO2 to CaO ratio of at least 1. It discloses an example where the melting temperature is 1,450° C.
Patent Document 1: U.S. Patent Application, Publication No. 7169206